A single edge razor is the way to go. If that makes you uncomfortable, use a credit card. The razor works a lot better though. I put mine in a net breeder and had the return from a sponge filter emptying into it so it got fresh water circulation all the time until they hatched. I didn't want to use the return from the power filter as I assumed that would be too much current when the eggs hatched. I think mine too about a week to hatch then I gave them a day to use up the yolk and started feeding them hikari first bites. I have about 60 or so juvie cories now.